In the art of shingle manufacture, particularly shingles for roofing, it has been known to manufacture shingles of bitumen-impregnated mat, with the mat often being of fiberglass construction, and with granules being applied to the bitumen-covered surface of the shingle, often with smaller granules, such as mica or the like, applied to the rear surface of the shingle, also held in place by bitumen on the rear surface of the shingle. Examples of such shingle manufacturing techniques are set forth in U.S. Pat. No. 4,295,445. U.S. Pat. No. 5,181,361, and U.S. Pat. No. 5,501,056, for example.
It is also known that shingles can be molded from hardenable materials, to simulate natural slate, wood shakes, or other natural materials. An example of molding shingles in the form of tiles is, for example, set forth in U.S. Pat. No. 6,178,703. In that patent, the material of shingle tile formation is essentially a clay, which hardens in a cement-like manner, to yield a fairly heavy shingle.